Given an image, it is often useful to find any other similar images. For example, a library of images may be provided where it is useful to find images of interest in the library. These images of interest may be images that are related to a given image. One application of this technique is the detection of copyright violations. Other applications include the location of image art for creative works, license retrieval or image identification. Image matching techniques such as these typically involve extracting one or more features from a given image and then directly matching said features against features for other images.